Redox

Oxidation number (Oxidation)

Increase in oxidation number

Oxidation number (Reduction)

Decrease in oxidation number

Rules for assigning oxidation states

1. Simple ions, oxidation state is the charge on the ion

2. For atoms in elements, oxidation state is zero

3. For compounds the sum of oxidation state is zero

4. Covalent molecules are assumed to be ionic

Exception to rules

1. Hydrogen in metal hydrides is -1

2. Oxygen in peroxides (H₂O₂) is -1

3. Oxygen bonded to fluorine, oxygen is +2

4. Other halogens become positively charged when bonded with O

Disproportionate reactions

A species is simultaneously oxidised and reduced`

Oxidising agent

Species that removes electrons from another

Reducing agent

Species that gives electrons to another